1. Field of the Invention
Exemplary embodiments of the present invention relate to a communication system; and, more particularly, to a signal transmitting apparatus and method for transmitting signals with different frequency bands.
2. Description of Related Art
In general, wireless communication systems define the standards for communication between a signal transmitting apparatus (or a transmitter) and a signal receiving apparatus (or a receiver). Therefore, the signal transmitting apparatus and the signal receiving apparatus have a predetermined frequency band for signal transmission.
Currently, a general wireless communication system uses one predetermined frequency band. For example, a Code Division Multiple Access (CDMA) communication system spreads signals by a random code prior to transmission. The CDMA communication system performs communication by using a predetermined frequency band. Also, an Orthogonal Frequency Division Multiplexing (OFDM) communication system transmits signals by using a plurality of subcarriers orthogonal to each other. The OFDM communication system may not use some of all the subcarriers. However, the OFDM communication system also has a predetermined frequency band for communication between a transmitting apparatus and a receiving apparatus.
In this manner, the conventional wireless communication systems transmit signals by using one radio frequency (RF) transmitter. However, a variety of next-generation wireless communication systems are to use various frequency bands (not a predetermined frequency band) for efficient use of limited frequency resources. An RF transmitter, which performs a radio signal processing operation for signal transmission through an antenna, can perform a radio signal processing operation only in a limited frequency band.
Thus, the next-generation wireless communication systems, which use a plurality of frequency bands (not a specific frequency band), must have additional RF transmitters corresponding to a plurality of frequency bands in order to communicate signals.